Prior to and during an operation of a patient placed on the patient support, the patient support is brought to a position which facilitates a surgical intervention on the patient. For this purpose, pivoting of the patient support by large angles may be required. Also the height of the operating table's patient support should be adjustable within a range as wide as possible. The operating table ideally further allows even for very small heights of the patient support, which requires compact construction of the operating table column.
The following three different types of operating tables are typically used in hospitals: stationary operating tables, movable operating and mobile operating tables. Stationary operating tables have an operating table column permanently fixed to the floor of an operating room, they normally do not comprise an operating table base, and energy is supplied to them via fixedly installed cables. With these stationary operating tables, the patient support can easily be detached and re-attached and is transportable by means of a dedicated transport apparatus. With this transport apparatus, a patient resting on the patient support can be transported to and away from the operating room.
Movable operating tables have an operating table base connected to the operating table column and allowing for free positioning in the operating room, and a patient support which can be detached from and re-attached to the operating table column. Moving of the operating table column is performed by means of a column transporter provided therefore, or, in the case of self-mobile movable operating tables, by means of incorporated extractable transport rollers.
Operating table bases of mobile operating tables include rollers for moving the operating table such that they can be moved without auxiliary means and are suited for transporting a patient. Further, with mobile operating tables, the patient support usually is coupled to the operating table column and is not separated from the operating table column in hospital practice.
Stationary operating tables as well as movable operating tables or mobile operating tables may employ components which can be adjusted by means of an electric motor, such as an operating table column which is length adjustable by means of an electric motor for height variation of a patient support attached to the operating table column, an operating table column head which is adjustable about two orthogonal axes for variation of tilt and swing of the patient support connected to the operating table column head, and/or components of the patient support that can be adjusted by means of an electric motor.
In particular during a surgical intervention on the patient, the operating table has to be supported in a stable and precise manner. For example, it must be capable of holding exterior forces and torques caused by lateral forces or by a change of the position of the patient's and the patient support's center of gravity without yielding noticeably. On the other hand, it must be guided in a manner so precise that height adjustment is possible without jamming of the elements provided for height adjustment.
For adjusting the height of an operating table column sliding guides are known having circular as well as non-circular cross sections. Great manufacturing efforts are required for producing a guide with non-circular cross section having only small clearance. Small clearance, however, is required for achieving high rigidity of the operating table. Use of a sliding guide with circular cross section has a disadvantage in that the element sliding on the guide may rotate about the longitudinal axis of the guide. In order to avoid such rotation, keys may be provided that engage in a groove and are arranged at the sliding element or the guide, respectively, and that accommodate torques acting about the longitudinal axis of the guide. This makes the production expensive and complex. Furthermore, the distance of the anti-twist protection is limited to the radius of the circular guide and requires great guide diameters for achieving the desired rigidity. In the case of an alternative construction, wherein two circular guides are arranged parallel to one another, the element sliding on the circular guides tends to jam when the typical manufacturing and mounting tolerances are considered.